Many types of electronic devices such as microprocessors, digital signal processors, memory devices, application-specific integrated circuits (ASICs) and the like typically terminate their input/output (I/O) signals to reduce signal reflections which occur at high frequencies. Reducing signal reflections reduces interference. An I/O signal is typically terminated by coupling the signal to a termination circuit such as a terminating resistor, which in turn is coupled to a termination voltage node. The termination circuit provides a termination voltage to the I/O signal which helps to reduce signal reflections at high frequencies. However, some electronic devices perform both high and low frequency operations where substantial signal reflections occur only at high frequencies and not low frequencies.
Take, for example, a conventional DRAM (dynamic random access memory) device. During normal operation such as reads and writes, its I/O signals operate at high frequencies to boost performance. Termination circuitry coupled to the I/O signals reduces interference caused by signal reflections which arise at high frequencies. DRAM devices also periodically perform a refresh operation to prevent data loss. The I/O signals of the DRAM device do not operate at high frequencies during a refresh operation. Instead, the I/O signals are typically held at a fixed voltage level while the refresh operation is performed.
One type of DRAM refresh operation is a self-refresh where the DRAM device is externally instructed to perform a refresh. For example, a GDDRx SDRAM (graphics double-data-rate synchronous dynamic random access memory, version x) can be instructed to perform a self-refresh operation by driving its chip select (CS), row address strobe (RAS), column address strobe (CAS) and clock enable (CKE) input signals low and its write enable (WE) input signal high at the rising edge of the clock input. However, the CKE input signal is typically terminated at a high voltage level. This causes static current to flow between the termination node and CKE input signal during the refresh operation because the CKE signal is held at a voltage level different than its termination voltage. For some DRAM devices, the CKE input signal draws approximately half of the total current consumed by the DRAM device during a self-refresh operation due to the termination-to-signal voltage mismatch. Generally, any I/O signal of an electronic device having a termination-to-signal voltage mismatch during a low-frequency operation (i.e., an operation which does not cause substantial signal reflections) unnecessarily draws current during the low frequency operation.